Magnetic resonance imaging is an imaging method in which atomic nuclear spins of a subject who is placed in a static magnetic field are magnetically excited with a radio frequency (RF) pulse at the Larmor frequency, and from a magnetic resonance signal generated in association with the excitation, an image is reconstructed.
As for cardiac study by magnetic resonance imaging, a standardized protocol has been defined. For example, the standardized protocol defines a sequence in which, after acquiring scout images (locator images) (for example, transverse section images (axial images), sagittal section images (sagittal images), and coronal section images (coronal images)), multi-slice images that are a plurality of transverse section images are acquired, and then reference cross-sectional images are acquired. The reference cross-sectional images are cross-sectional images based on anatomical characteristics of heart, and the examples thereof include, but are not limited to, left ventricular vertical long-axis images, left ventricular horizontal long-axis images, left/right ventricular short-axis images, left/right ventricular 2-chamber long-axis images, left/right ventricular 3-chamber long-axis images, left/right ventricular 4-chamber long-axis images, left/right ventricular outflow tract images, aorta valve images, and pulmonary valve images. In the study of target regions other than the heart such as “brains” and joints such as “shoulders” and “knees”, there are sequences equivalent to the above-described acquisition of the reference cross-sectional images.
Conventionally, the operation of positioning reference cross-sectional images has been a problem. For example, there are methods that automatically detect cross-sectional positions of the reference cross-sectional images by determining a blood region of ventricles from the images, and by detecting the axis of the heart from the multi-slice images. In these methods, however, the accuracy of automatically detected cross-sectional position may deteriorate due to a time lag between the acquisition of multi-slice images and the acquisition of each of the reference cross-sectional images. For example, if the body of a subject is moved after the acquisition of multi-slice images during the acquisition of respective reference cross-sectional images, the cross-sectional positions of the subsequently acquired reference cross-sectional images are all displaced.
Meanwhile, in the case of manual positioning as defined in the standardized protocol, for example, because the positioning is a method in which the reference cross-sectional images acquired immediately before are used to position a subsequent reference cross-sectional image, the risk of deterioration in the accuracy of cross-sectional position by the time lag is low. The manual method, however, is very cumbersome, and is also inefficient because even the cross-sectional images not necessary for diagnosis have to be acquired for the positioning of reference cross-sectional images.